Electric system



Feb. 22, 1944. EDGERTON 2,342,257

ELECTRIC SYSTEM Filed April 28, 1941 INVENTOR Egg-fig? Efdggpim ATTORNEYPatented Feb. 22, 1944 UNITED STATES PATENT OFFICE 2,342,251 ELECTRICSYSTEM Harold Eugene Edger-ton, Belmont, Mass.

Application April as, 1941, Serial No. 390,723

I 21 Claims. (01. ale-ass) The present invention, though having fieldsof more general usefulness in electric systems, is particularly relatedto stroboscopes and to the production of intermittent or flashing light.The present application is a continuation-in-part of application, SerialNo. 685,501, filed August 16, 1933.

An object of the invention is to provide a new and improved electricsystem and a new and improved stroboscope of the above-describedcharacter.

Other and further objects will be explained hereinafter and will beparticularly pointed out in the appended claims. The invention will nowbe described in connection with the accompanying drawing, the singlefigure of which is a diagrammatic view of circuits and apparatusarranged and constructed according to one embodiment of the invention,illustrating a stroboscopic light source operated by alternatingcurrent, but capable of operatmg at any flashing frequency.

A- mercury-arc gaseous-discharge-lamp is illustrated as provided withtwo internal electrodes in a glass tube envelope 2. These tubes arenormally non-conductive. The remarks throughout this specificationconcerning mercury-arc stroboscopes apply equally well to tubes filledwith other gases, with or without mercury vapor.

One of the internal electrodes is in the form of a liquid pool 4 ofmercury, used for a cathode, and the other serves as the anode B. If,other than mercury-arc tubes are employed, other substances, such asaluminum, barium, iron, etc., or various combinations of elements, mayalso be employed as the cathode. An external, metallic grid or controlelectrode I is situated around the glass, outside of the mercury pool 4,opposite to the meniscus of the mercury, and serves as a starting bandfor facilitating the starting of the tube. Other types of starting bandsmay be employed. It is also possible to employ an internal grid orcontrol electrode which, like the electrode I00, may be excited from thesecondary winding 29 of a transformer of any desired type, such as aflashing, high-ratio, step-up transformer 30. A voltage will beaccurately and reliably applied to the primary winding 36 of thetransformer 30 from a source of direct-current voltage, so as to betransmitted to the external grid or electrode I00, thereby accuratelyand reliably starting the mercury-arc tube 2. The source ofdirect-current. voltage is shown as supplied from a common type offull-wave, thermionic, rectifier-and-fllter circuit, comprisingthermionic or gaseous-discharge rectiflers 20 and 22, connected with anydesired source I of alternating energy of suitable voltage and frequencyin any well-known manner, as by means of a secondary winding H! of atransformer I48. The secondary winding H1 is shown connected to theanodes of the rectifier tubes 20 and 22. The conductor In is shownconnecting the anode 6 to one end of the secondary winding 1, throughthe rectifier tube 20. A main discharge capacity or condenser 26 isnormally charged to the full potential of the rectifier. A filtercondenser 25 is provided as part of the source of direct current, largein capacity when compared to the condenser 25, the function of which isto maintain a supply of energy between the pulses of power given by therectifier units 20 and 22 to the load 2.

The cathode 4 and the anode 6 of the normally non-conducting mercury-arcstroboscope tube 2 are connected in the output circuit of the tube 2,directly across the condenser 26, in any desired manner, as by means ofwire conductors 8 and I0. A current-limiting, charging impedance 35 isemployed, which may be constituted of a wire conductor. This conductoror impedance 35 is usually a combination of resistance and inductance,

and is large enough to hold back the current until the tube hasdeionized, but small enough to allow the condenser to charge in time forthe next flash.

The condenser 26 is charged from the said directcurrent source ofvoltage by connecting it to the secondary winding i4! through therectiflers 2c and 22. The series circuit consisting of the impedance 35and the condenser 26 may be oscillatory, non-oscillatory, or criticallydamped, as desired; the use of both oscillatory and non-oscillatorycondenser charging circuits is already known to the art. The impedance35 may be chosen so that its resistance and inductance shali have suchmagnitude relative to the capacity of the condenser 26 that the chargingcircuit shall be oscillatory. There is nothing critical concerning thecharging circuit, however, except when the natural period of the seriescircuit or the time constant is appreciable when compared to theinterval of time between flashes.

The impedance 35 connects the cathode 4 and one end of the condenser 26'to the negative end of the before-mentioned direct-current source ofvoltage. The impedance 35 may, however, be connected in series with theanode 6, in the positive side of this source. The anode 6 and the otherend of the condenser 26 are connected to the positive end of. thedirect-current source.

the anode is positive. If the mercury-arc tube 2 has been exhaustedadequately, it will not conduct current when the condenser is charged,notwithstanding the difference of potential between the cathode 4 andthe anode 6. The usual voltage to which the condenser is charged is from200 to 2,000 volts.

The quantity of stroboscopic light is determined by the amount of energyin the condenser 33 and by circuit conditions. The capacity of thecondenser 23 is increased, as by varying the condenser 23 or by means ofadditional condensers 21 until there is sufficient average light for theparticular frequency of flashing and the extraneous illumination. Theadditional condensera 21 may be connected by means of switches 3 and I,in parallel with the condenser 26, thus to increase the brightness offlash. Slow speeds require a larger amount of light per flash than fastspeeds to give the same average illumination. The amount of light perflash may be varied also by changing the value of a series resistor IIin the lamp-discharge circuit, as well as in other ways.

In order to obtain sudden surges of current through the primary winding36 of the flashing transformer 30, a timing relay is employed. Thetiming relay is preferably in the form of a normalLv non-conductingmercury-vapor thyratron trigger tube I43, or other gaseous-dischargedevice, such as a gas-filled hot-cathode thermionic tube, or agrid-controlled cold-cathode arc-discharge tube, connected with thetransformer in such a manner that, when it operates, the energy in asmall condenser 23 is discharged at selected intervals into thetransformer 30, whenever the tube 2 is to be set into operation. As thetube I43 conducts in one direction only, it serves as a check valve. Itis a gaseous-conductor device having at least three electrodes, namely,a cathode 43, a grid 03 and a plate 52, and may be of a type in whichthe maximum potential which can be established between the two mainelectrodes 43 and 63 without appreciable current flow therebetween maybe controlled by controlling the potential between one of the mainelectrodes, namely, the cathode 43, and the third electrode 33. Thecurrent between the anode 33 and the cathode 43 may be controlled, andthe electric discharge between them may be imtiated, by varying thepotential of the third electrode II with respect to the cathode 43.

The trigger thyratron tube I40 is connected across a bleeder resistor33, so as to be supplied with voltage therefrom. The bleeder-resistor 33thus serves as a source of energy for the condenser also. The bleederresistor 33 is connected. in series with an impedance, which ispreferably constituted of a bleeder resistor 31, across the condenser33, which constitutes the main power-supply for the tube I40. Power forthe tube I40 may, however, be obtained, if'desired, from a separatepower-supply. The resistors 3I and 33 may be so proportioned that adesired voltage of. say. 300 volts shall appear across the resistor 33.The bleeder resistance 33 allows a small current to flow, in order tomaintain the proper voltage bias upon the grid 30 and its resistance isnecessary to prevent the self operation of the thyratron I40 when thecondenser 28 becomes fully charged. By reason of the connection of thegrid 50 to the conductor 8, advantage is taken of the negative biasacross the resistor 3| to keep the tube I40 ineffective until an impulseis applied to the grid 50.

The secondary winding 29 of the transformer 301s shown connected in theinput circuit of the tube 2, between the cathode 4 and the externalelectrode I00, to produce the high-voltage triggering action. Theprimary winding 38 of this transformer is connected, in series with thecondenser 28, in the power output or control input or plate circuit ofthe thyratron I40, between the cathode 48 and the plate or anode 52. Theprimary winding 36 is thus connected in parallel with the tube I40 butin series with the condenser 20. The power output circuit, whilenormally dpen, because of a normally negative bias on the grid 50,becomes essentially short-circuited whenever the grid 50 s subjected toa suitable stimulus.

The condenser 28 may be charged from the same direct-current source ofvoltage, or from any other suitable voltage supply, through thepreferably resistive impedance 3 I, in series therewith. The impedance3i may, however, be inductive, or a combination of resistance andinductance. The condensers 26 and 28 are both charged from the saiddirect-current source through the impedance 35, the condenser 23 throughthe resistor 3i. If the impedance is reactive, or if there are othercircuit conditions such that the grid voltage exceeds the criticalstarting potential, the thyratron circuit may, under certain conditions,generate its own oscillations at a frequency determined by the circuitconstants and the characteristics of the tube. The impedance, 3I may bemade adjustable,'as illustrated, in order to vary the charging rate ofthe condenser 28 and this, in turn, regulates the frequency of the'high-voltagesurges that are applied to the external electrode I00. Theimpedance 3| of Fig. 1, in addition, prevents a destructive discharge ofthe condenser 20 through the thyratron I40, in case the stroboscopictube 2 fails to function. The resistor 33 is made to have a large value,or is disconnected, when selfoscillaticns of the thyratron I40 aredesired. The grid 50 may be connected to various taps on the resistance33 or 3|, to cause the thyratron to oscillate as a relaxationoscillator. In all cases, the grid 50 is normally negative with respectto the cathode 48.

The self-excited relaxation-oscillator thyratron circuit described inthe preceding paragraphs as initiating, discharge of the condenser 26 atselected intervals is sometimes termed a self-excited static inverter.This inverter produces electrical impulses at a controlled ratedetermined by its adjustment. If an external signal is used to trip thethyratron, the circuit is sometimes called a driven static inverter.

The manner of connecting the grid for selfoscillation depends upon thecharacteristics of the particular thyratron that is used. Thyratrons,furthermore, especially the inverter types that have a shortdeionization time, require a certain amount of grid current in order toconduct. Often a positive voltage is required on the grid of anegative-control thyratron to supply the required grid current through agrid resistor I42, connected between the controlled grid 00 and thegrid-biasingresistor 3i. The grid reslstor I42, if varied, will vary theself-oscillation rate, if grid currents are necessary for starting.

The use of the thyratron tube I40 makes it possible to operate thecircuit without any moving parts, except, in some cases, for causing thethyratron to function. The thyratron does not conduct current whenthere' are no impulses in the grid circuit, except when used forself-oscillation, as described. A timing impulse coming into the inputor grid circuit; to stimulate the grid 50, trips the thyratron I40,establishing a high-potential gradient between the electrode I and thecathode 4, thereby causing starting of the tube 2. The time of startingis controlled by the potential on the grid 50.

The flashes of light are illustrated as controlled through the closingof a switch 32 which may, of course, be controlled by a periodicallymovable member, as described in Letters Patent 2,181,879, issuedDecember 5, 1939. The switch 32 may be very small, sinceit causes verysmall currents. The grid 50 of the thyratron I40 is connected to oneside of the switch 32 through a small trip condenser 59, which may be assmall as 0.00025 microfarad. The other side of the switch 32 isconnected to the anode 52. The grid 50 is also connected to the negativeend of the resistor 3|, in series with the resistor I42. The resistorI42 limits any current that may tend to flow when the grid 50 becomespositive, or when there is any ionization in the tube. When the switch32 is closed, therefore, at any time after the voltage across thecondenser 26 reaches its maximum value, the grid 50 of the thyratronbecomes positive with respect to the cathode 48 to a value greater thanthe breakdown voltage between the grid 50 and the cathode 48, whereuponthe thyratron becomes conductive.

At the instant that the grid potential, in response to the action of theswitch 32, reaches the critical value, positive with respect to thecathode 48, in response to the stimulus applied to the grid 50, theoutput circuit of the thyratron I40 is completed from the anode 52 tothe cathode 40, through the primary winding 36 and the condenser 28. Theenergy stored in the condenser 28 is then suddenly discharged intothelow-impedance primary winding 36 of the stepup transformer 30, throughthe output circuitof the thy'ratron tube I40. This magnetically inducesa high voltage for a brief interval of time in the secondary winding 29.A high voltage is thus suddenly applied to the electrode I00. A surge ofcurrent is caused to flow through the resistor I42. The cathode 48 isthus raised to nearly the potential of the anode 52 during discharge,and the grid 50 is given a sudden and very strong negative bias.

This suddenly applied, relatively high voltage produced by the potentialon the grid 50 across the terminals of the secondary winding 29 willcause a bright, cathode spot to form on the surface of the mercurycathode 4 and at the junction between the mercury and the inner wall ofthe glass tube. The gas in the tube becomes thus ionized. The brightspot constitutes a source of electrons in the vicinity of the cathode 4that supplies electrons for the discharge of the condenser 26 throughthe tube 2 between the anode 6 and the cathode 4.

An arc discharge is thus abruptly initiated through the-tube 2. Abrilliant flash of light is, therefore, produced by the mercury-pooltube 2 when'the condenser 26, after being charged to a certain value,discharges its energy violently and quickly into it at the desiredinstant, in response to the stimulus produced upon the band electrodeI00 by the impulse surge in the secondary winding 28 of the flashingtransformer 30. The potential upon the grid 60 controls the time ofstarting of the violent, electrical transients that are transformed intouseful light.

At the instant of discharge, the current surge is naturally very large,over one thousand amperes, and the flash of light through the tube isvery intense and quick. The apparent speed of a moving object is thuseffectively reduced or stopped, since the object moves an inappreciabledistance during the time that the light is on. Because .of the lowimpedance of the mercury lamp 2, the voltage across the resistor 33 iszero after the condenser 26 has become fully discharged, preventing thecondenser 20 from charging again, and allowing the tube to deionize; andthe duration of the flash discharge is short, the time taken for thecircuit to function from the closing of the contactor 32 to the flash oflight from the tube 2 being about 10 microseconds or less, the exacttime being a function of the size of the capacity 26, the voltage towhich it is charged, the dimensions of the tube, the temperature of thetube, the impedance of the leads 8 and I0 connecting the condenser andthe tube, the volt-ampere characteristics of the tube 2, and otherfactors. Under some conditions, the duration of the flash is less thanone microsecond.

Immediately after the condenser 28 discharges, the grid 50 is caused tobe very negative with respect to the cathode 48, and, in this manner,the thyratron is preventedfrom starting as the condenser 28 builds upand the anode becomes positive with respect to the cathode.

The impedance of the conductors 8 and I0 is useful in extinguishing thearc. As soon as the current in the thyratron circuit stops, the currentin the tube 2 will not be established in the,

opposite direction; for, since there is no source of electrons on theanode 6, mercury-arc tubes do not reverse in their normal operation. Theare, therefore, becomes extinguished. As the tube 2 permits current toflow only from the anode 6 to the cathode 4, it acts as a rectifier.After the tube 2 extinguishes, the cycle is ready for repetition.

The condenser discharge through the mercuryvapor lamp 2 would beoscillatory except for the fact that the tube 2 is a rectifier. Thisoscillatory tendency is useful, however, since it assists in preventinga continuous flow of current through the lamp 2 from thebefore-described direct-current power supply. The condenser 26 ischarged with a potential of an opposite polarity after a surge ofcurrent flows through the tube 2. A negative voltage is thus put on theanode 6, which helps to deionize the tube.

As the thyratron I40 is a rectifier, the current in the circuitcomprising the condenser 28 and the transformer 30 cannot oscillate,although there is a tendency to do so. At the instant that the currentstops, due to the oscillation, the tube I40 begins to deionize, sincethe grid and plate voltages, at this instant, are both either negativeor zero with respect to the cathode 48. The charging current of thecondenser 28 causes a voltage drop acrossthe resistance 3|, which isnegative with respect to the cathode 48. This voltage drop is nearlyequal to the voltage of the direct-current supply at the first instant,but becomes smaller as the condenser 28 is charged.

The condenser 24 then recharges from its source of voltage, through theimpedance II, in preparation for the next impulse.

The thyratron trip circuit puts a high voltage on the starting band I"ina sudden manner that makes the tube start reliably. The use of thisstarting-tube thyratron makes the mercuryarc stroboscope a practical anduseful arrangement. The mercury-arc tube may thus be started by a fewmicroamperes of current in the grid circuit of the control tube, andthere is a negligible time delay between the current impulses to thegrid and the starting of the light flashes.

Tripping surges in the grid circuit can be supplied either bytransformer or capacity coupling, as commonly used in the art. Theresistance Il may be made to have a high value; or it may be opencircuited, if self-oscillations are desired.

The gaseous-discharge device I40 is shown connected in circuit with thesource of potential and with the variable impedance 33 or Ii. Thevoltage impulses which occur at the instant that current flows throughthe electric check valve I40 are, in both cases, conveyed through thetransformer 30 to the flash-producing apparatus 2.

A leak resistor I43 may be put across the condenser in the grid circuitto discharge it between successive transients, between flashes, as atthe opening of the switch I2, in order to prepare for the next surge,but the value the resistance of the leak is sufliciently high to preventfurther influence upon the thyratron if the switch 32 is left in aclosed position. The connections may thus be traced from the grid 50,through the blocking condenser 50 and the leak resistor I43, inparallel, the contactor l2, and the primary winding 38, to the anode 52.The trigger tube i4! is thus, through the contactor 32, connected to itsgrid 50, caused to flash the hashlamp II at the desired instant. Afterdischarge, the grid 50 again becomes negative with respect to thecathode 48.

Once the switch 32 becomes closed, it may remain closed without thetlwratron I40 flashing on again when the condensers 26 and 24 build uptheir voltages. The operation is independent of the length of time thatthe switch 32 remains closed, for the complete function is performed atthe moment of first closing.

An adjustable impedance l8, shown as a resistance, is convenientlyconnected into circuit, especially in variable-speed stroboscopes, asbetween the cathode 44 and the impedance 3|, for varying the intensityof the starting voltage which is applied to the starting grid Hill. Theimpedance I9 and the transformer 40 may be in either the anode or thecathode circuit. The impedance i9 is adjusted.until sumcient voltage isobtained to make the operation satisfactory.

The circuits of the present invention are useful for mam! other purposesthan for the production of stroboscopic light. They are useful withalmost any apparatus adapted for excitation by electrical impulsesthrough the medium of a condenser.

Modifications will occur to persons skilled in the art, and all such areconsidered to fall within the spirit and scope of the invention, asdefined in the appended claims.

What is claimed is:

l. A flash-lamp. system comprising a hashlamp, a first source 01'energy. a discharge condenser, a trigger tube, a second source of energyfor the trigger tube comprising a bleeder resistor.

means connecting the flash-lamp to the discharge condenser, meansconnecting the discharge condenser to the first source of energy tocause the discharge condenser to become charged from the first source ofenergy, means connecting the second source of energy to the trigger tubeto supply energy to the trigger tube, means connecting the trigger tubeto the flash-lamp, and means for discharging the discharge condenserthrough the flash-lamp under the control of the trigger tube.

2. A flash-lamp system comprising a flashlamp, a condenser fordischarging through the flash-lamp, a charging circuit for connectingthe condenser to a source of energy, a gaseous-discharge trigger devicecomprising an anode, a cathode and a grid, 9. second condenser, ableeder resistor for charging the second condenser, means connecting thesecond condenser to the anode and the cathode, means for controlling thegrid to cause the second condenser to discharge through the dischargedevice, thereby to cause the first-named condenser to discharge throughthe flash-lamp to eflect flashing of the flash-lamp, and means forreducing the voltage across the bleeder resistor," to substantially zerowhen the first-named condenser discharges through the flash-lamp.

3. A flash-lamp system comprising a flashlamp, a condenser fordischarging through the flash-lamp, a charging circuit for connectingthe condenser to a source of energy, a gaseousdischarge trigger devicecomprising an anode, a cathode and a grid, a second condenser, a bleederresistor for charging the second condenser, a second resistor, meansconnecting the resistors in series across the first-named condenser,means connecting the second condenser to the anode and the cathode, andmeans for controlling the grid to cause the second condenser todischarge through the discharge device, thereby to eflfect flashing ofthe flash-lamp.

4. A flash-lamp system comprising a flashlamp, a condenser fordischarging through the flash-lamp, a charging circuit for connectingthe condenser to a source of energy, a gaseous-discharge trigger device,a second condenser, a transformer having a primary winding and asecondary winding, a bleeder resistor, means connecting the bleederresistor to the first-named condenser to supply energy from thefirst-named condenser to the bleeder resistor, means connecting thesecond condenser and the primary winding to the bleeder resistor as asource of energy, means connecting the secondary winding to theflash-lamp, and means for discharging the second condenser through thegaseousdischarge device, thereby causing the first-named condenser todischarge through the flash-lamp.

5. A light-flash producer having, in combination, a gaseous-dischargelamp that 1 mally non-conducting when not in operation and throughwhich, when the lamp is conducting, a discharge may pass to produce aflash of light of substantial illumination intensity, means forconnecting the device to a source of energy, means for producing thesaid discharge from the source when the lamp is conducting, a gas-filleddevice through which a discharge may pass to render the lamp conducting,a second source of energy for the gas-filled device comprising a bleederresistor, means for connecting the bleeder resistor to the first-namedsource to supply energy from the first-named source to the bleederresistor. and means comprising a condenser for producing a dischargefrom the second-named sound through the gas-filled device.

6. A light-flash producer having, in combination, a gaseous-dischargelamp that is normally non-conducting when not in operation and throughwhich, when the lamp is conducting, a discharge may pass to produce aflash of light of substantial illumination intensity, means forconnecting the device to a source of energy, means for producing thesaid discharge from the source when the lamp is conducting, a gasfilleddevice having a control input circuit that is normally unenergized whenthe device is not in operation and an output circuit through which adischarge may pass to render the lamp conducting when the input circuitis energized, a second source of energy for the gas-filled devicecomprising a bleeder resistor, means for connecting the bleeder resistorto the first-named source to supply energy from the first-named sourceto the bleeder resistor, and means for energizing the control inputcircuit.

I. A light-flash producer having, in combination, a gaseous-dischargelamp that is norgas-filled device comprising a bleeder resistor.

means for connecting the bleeder resistor to the first-named source tosupply energyfrom the first-named source to the bleeder resistor, meansfor producing a discharge through the device,

the device having a control electrode that is nornot in operation andoperative when effective to render the device conducting to enact adischarge of energy from the source through the device. agaseous-discharge rectifier that is normally inefl'ective when therectifier is not in operation and having an anode, a cathode and acontrol electrode the rectifier being operative when efl'ective torender the normally ineffective means efiective, a second source ofenergy for the rectiller comprising a bleeder resistor, means forconnecting the bleeder resistor to the first-named source to supplyenergy from the first-named source to the bleeder resistor, means forproducing a transient impulse upon the control electrode, and meansoperable in response to the transient impulse upon the control electrodefor rendering the rectifier suddenly effective, thereby to render thenormally'ineilective means suddenly eilective.

10. An electric circuit comprising a load, a source of energy for theload, a grid-controlled tube, 'means for connecting the tube to thesource, means for connecting the load to the tube, means for biasing thegrid of the tube, an impedance connected between the grid and thebiasing means, a condenser for controlling the said grid connected tothe impedance and the said grid, and means comprising a switch forconnecting the condenser to a source of energy to cause the condenser tobecome charged to energize the grid.

11. An electric circuit comprising a load, a

' source of energy for the load, a grid-controlled tube, means forconnecting the tube to the source,

' means for connecting the load to the tube, means connected to theimpedance and the said grid,

mally ineflective when the device is not in operation for initiatingwhen eilective the operation tion and comprising at, least two principalelectrodes and a control member associated with one of the principalelectrodes for rendering the electric valve conductive between theprincipal electrodes. a source of potential, means for connecting theprincipal electrodes to the source. a capacitance, a-grid-controlledgas-filled electric valve, a second sourceof potential for thegridcontrolled valve comprising a bleeder resistor, means for connectingthe bleeder resistor to the first-named source to supply energyfrom thefirst-named source to the bleeder resistor, means for charging thecapacitor from the second source. and means comprising thegrid-controlled valve for transmitting a relatively large transientelectrical impulse through said control member and said capacitance torender conductive said first-mentioned electric valve.

9. An electric system having, in combination, a gaseous-discharge devicethat is normally nonconducting when not in operation, means forconnecting the device to a source of energ means normally ineffectivewhen the device is an additional impedance, and means comprising aswitch for connecting the condenser through the additional impedance toa source of energy to cause the condenser to become charged to energizethe grid.

12. An electric circuit comprising a load, a source of alternatingenergy, a condenser connected to the source. a filter for filteringalternating-current ripples out of the condenser. a grid-controlledtube, means for connecting the tube to the condenser, means forconnecting the load to the tube. means for biasing the grid of the tube,an impedance connected between the grid and the biasing means, acondenser for controlling the said grid connected to the impeditmavconstitute a source of energy, means for char ing the second condenserfrom the bleeder resistor. means for connecting the second condenser tothe anode and the cathode to energize the trig er device from thebleeder resistor. means for controlling the control electrode to causethe second condenser to discharge through the trigger device. means forconnecting the first-named condenser to the flash-lamp, and means forcausing the first-named condenser. after it has become charged, todischarge through the sash-lamp when the second condenser dischargesthrough the trlller device.

14. A lit-fiash-producer having, in combination, a gaseous-dischargelamp that is normally non-conducting when not in operation and throughwhich, when the lamp is conducting, a discharge may pass-to produce aflash of light or substantial illumination intensity, means forconnecting the device to a source of energy, means for producing thesaid discharge from the source when the lamp is conducting, means forrendering the lamp conducting, a second source of energy for therendering means comprising a bleeder resistor, and means for connectingthe bleeder resistor to the first-named source to supply energy from thefirst-named source to the bleeder resistor.

15. A light-flash producer having, in combination, a gaseous-dischargelamp that is normally non-conducting when not in operation and throughwhich, when the lamp is conducting, a discharge may pass to produce afiash of light of substantial illumination intensity, means forconnecting the device to a source of energy, means for producing thesaid discharge from the source when the lamp is conducting, a gas-filleddevice through which a discharge may pass to render the lamp conducting,a second source of energy for the gas-filled device comprising a bleederresistor, means (or connecting the bleeder resistor to the first-namedsource to supply energy from the first-named source to the bleederresistor, and means for producing a discharge from the second-namedsource through the gasfilied device.

16. In combination, an electric valve that is normally non-conductingwhen not in operation and comprising at least two principal electrodesand a control member associated with one o! the principal electrodes forrendering the electric valve conductive between the principalelectrodes, a source of potential, means for connecting the principalelectrodes to the source, a gridcontrolled gas-filled electric valve, asecond source of potential for the grid-controlled valve comprising ableeder resistor, means for connecting the bleeder resistor to thefirst-named source to supply energy from the first-named source to thebleeder-resistor, and means comprising the grid-controlled valve fortransmitting a relatively large transient electrical impulse throughsaid control member to render conductive said first-mentioned electricvalve.

17. In combination an electric valve that is normally non-conductingwhen not in operation and comprising at least two principal electrodesand a control member associated with one of the principal electrodes forrendering the electric valve conductive between the principalelectrodes, a source of potential, means for connecting the principalelectrodes to the source, a capacitance, a second source or potentialcomprising a bleeder resistor, means for connecting the bleeder resistorto the first-named source to supply energy from the first-named sourceto the bleeder resistor, means for charging the capacitor from thesecond source, and means comprising the grid-controlled valve fortransmitting a relatively large transient electrical impulse throughsaid control member and said capacitance to render conductive saidelectric valve.

18. In combination an electric valve that is normally non-conductingwhen not in operation, a source of potential, means for connecting thevalve to the source, a capacitance, a grid-controlled gas-filledelectric valve, a second source or potential for the grid-controlledvalve comprising a bleeder resistor, means for connecting the bleederresistor to the first-named source to supply energy from the first-namedsource to the bleeder resistor, means for charging the capacifor fromthe second source, and means comprising the grid-controlled valve fortransmitting a relatively large transient electrical impulse throughsaid capacitance to render conductive said first-mentioned electricvalve.

19. An electric system having, in combination, a gaseous-dischargedevice that is normally nonconducting when not in operation, means forconnecting the device to a source of energy, means normally inefiectivewhen the device is not in operation and operative when eflective torender the device conducting to efiect a discharge of energy from thesource through the device, a gaseous-discharge rectifier that isnormally inefiective when the rectifier is not in operation and having acontrol electrode, the rectifier being operative when eilective torender the normally inefi'ective means efiective, a second source oienergy for the rectifier comprising a bleeder resistor, means forconnecting the bleeder resistor to the first-named source to supplyenergy from the first-named source to the bleeder resistor, a switch,means whereby manipulation of the switch will produce a transientimpulse upon the control electrode, and means operable in response tothe transient impulse produced upon the control electrode onmanipulation of the switch for rendering the rectifier suddenlyeffective, thereby to render the normally inefi'ective means suddenlyeflective.

20. An electric system having, in combination, a gaseous-dischargedevice that is normally nonconducting when not in operation, means iorconnecting the device to a source of energy, means normally ineffectivewhen the device is not in operation and operative when efiective torender the device conducting to effect a discharge of energy from thesource through the device, a gaseous-discharge rectifier that isnormally ineffective when the rectifier is not in operation and having acontrol electrode, the rectifier being operative when eflective torender the normally ineffective means efi'ective, a second source ofenergy for the rectifier comprising a bleeder resistor, means forconnecting the bleeder resistor to the first-named source to supplyenergy from the first-named source to the bleeder resistor, a condenser,means for charging the condenser, a switch, means whereby manipulationof the switch will produce a transient impulse upon the -controlelectrode, and means operable in reconnecting the device to a source ofenergy,

means normally inefi'ective when the device is not in operation andoperative when efiective to render the device conducting to efi'ect adischarge of energy from the source through the device, agaseous-discharge rectifier that is normally ineffective when therectifier is not in operation and having a control electrode, therectifier being operative when efi'ective to render the normallyineffective means eflfective, a second source of energy for therectifier comprising a bleeder resistor, means for connecting thebleeder resistor to the first-named source to supply energy from thefirst-named source to the bleeder resister, a condenser, an impedance inshunt to the condenser, a switch, means whereby manipulation of theswitch will produce a transient impulse upon the control electrode, andmeans operable in response to the transient impulse produced upon thecontrol electrode on manipulation of the switch for thereupon causingthe condenser to discharge suddenly through the rectifier to render therectifier suddenly effective, thereby to render the normally ineflectivemeans suddenly effective.

HAROLD E. EDGERTON.

CERTIFICATE OF CORRECTION. Patent No. 2,5A2,257. February 22, 19th,.

HAROID EUGENE EDGERTON.

It is hereby certified that error appears in the printed specificationof the above numbered ,patent requiringcorrection as follows; Page 5,first column, line Claim 5, for the word "sound" read --source--; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of 'Hue case. in the PatentOffice.

Signed and sealed this 25th day of April, A. D. 191414..

Leslie Frazer (S Acting Commissioner of Patents.

